The breakdown of the watershed between the Firths of Clyde and Forth exposes southern Perthshire, the counties of Clackmannan and Kinross, and nearly the whole of Fife to the clouds and rains of the west, and their climates are consequently wetter than those of any others of the eastern slopes of the country.
We irrigate chiefly in the colder and wetter half of the year, and we " saturate " with water the soil in which are growing such plants as are perfectly content with earth not containing more than one-fifth of its weight of moisture.
And some misapprehension has been caused by the bare, but perfectly correct, statement that the general slope towards the western coast is wetter than that towards the eastern.
Pinus excelsa, which occurs in Bhutan, is absent in the wetter climate of Sikkim.
The truly tropical flora of the hotter and wetter regions of eastern India is continuous with that of the Malayan peninsula and islands, and extends along the lower ranges of the Himalaya, gradually becoming less marked and rising to lower elevations as we go westward, where the rainfall diminishes and the winter cold increases.
Between these two systems of hills lies the fertile undulating tract known as the Wetterau, watered by the Wetter, a tributary of the Main.
Speaking broadly, the general type of the flora of the lower, hotter and wetter regions, which extend along the great plain at the foot of the Himalaya, and include the valleys of the larger rivers which penetrate far into the mountains, does not differ from that of the contiguous peninsula and islands, though the tropical and insular character gradually becomes less marked going from east to west, where, with a greater elevation and distance from the sea and higher latitude, the rainfall and humidity diminish and the winter cold increases.